The present invention relates generally to the manufacture or building of tires by sequentially applying a plurality of concentrically disposed tire bands onto a tire building drum to form a multiple-ply tire carcass, and more particularly to an improvement in the apparatus for applying the bands onto the tire drum.
Tire carcasses utilized for the manufacture of tires are generally formed of a plurality of plies of rubber with suitable fillers and reinforcing material disposed between the plies. The tire carcasses are typically assembled by sequentially placing a selected number of elongated cylindrical tire bands onto a collapsible elongated cylindrical tire building drum to form a concentric, layered stack of tire bands, each of which defines a ply of the tire. After assembling the tire carcass, the cylindrical drum is collapsed and the tire carcass is removed for subsequent processing into the finished tire.
The placement of the tire bands onto the tire building drum to form the tire carcass has been previously achieved by employing several different types of apparatus. One such apparatus found to be particularly suitable for applying the desired number of concentrically disposed tire bands on the tire building drum is a selectively expandable/collapsible band applicator or applier. This band applier comprises a plurality of elongated, longitudinally extending rollers circumferentially spaced about and supported on a central longitudinally extending tube. The tube is cantileveredly supported at one end thereof by a horizontally pivotable housing and is longitudinally displaceable to move the rollers carried thereby along the rotational axis of the tire building drum for aligning the band applier with the tire building drum. The rollers are connected to the central tube by expandable and contractible scissor-like couplings which function to displace the elongated rollers radially away from or toward the centrally disposed support tube for varying the outer diameter of the band applier as defined by the outer surface of the elongated rollers. An elongated drive roller positioned at an angle to the rotational axis of the tire building drum is used for rotating and displacing the tire band from the band applier onto the tire building drum and is connected to the central tube by scissors-like couplings essentially similar to those used with the aforementioned rollers so as to be radially displaced along with these rollers during the expansion or contraction of the band applier. With the band applier in a collapsed condition, an elongated cylindrical tire band is placed in an encompassing relationship over a length of the elongated rollers and the drive roller. The band applier with the tire band thereon is then aligned with the tire building drum so that the central tube is coextensive with the rotational axis of the tire building drum. The central tube of the band applier along with the rollers attached thereto is then longitudinally displaced for moving the end of the band applier to a location contiguous to the outboard end of the tire building drum.
Coincident with or substantially coincident with the longitudinal displacement of the central tube, the band applier is radially expanded through a suitable drive coupled to the scissors-like couplings to provide the rollers on the band applier with an outer diameter in a range of slightly less than to slightly greater than the outer diameter of the tire building drum. The drive roller is canted at an angle to the rotational axis of the tire building drum to help displace the tire band from the band applier onto the tire building drum. The drive roller bears against the inside surface of the tire band and rotates the tire band at a rotational speed essentially corresponding to the rotational speed of the tire building drum and the tire band is moved longitudinally along the rollers by the angled drive roller and onto the tire building drum.
To facilitate movement of the tire band from the band applier onto the tire building drum, an elongated air nozzle is carried by the band applier at the leading end of the drive roller and is radially positionable with the drive roller. During the axial movement of the expanded band applier, the air nozzle is to be positioned at a location radially spaced from the outer surface of the tire building drum and any band previously placed on the drum surface. When a tire band is moved about half-way onto the tire building drum by the drive roller and extends over the air nozzle an air stream directed through the end of air nozzle will flow between the tire band being applied and the surface of the tire building drum or the outer surface of a previously applied band to assist in moving the band the remaining distance onto the tire building drum. The air nozzle, like the drive roller, is also canted at an angle with respect to the rotational axis of the tire building drum to help pull the leading edge of the tire band across the gap between the band applier and the tire drum until the air stream from the nozzle has a chance to start pushing the tire band onto the tire building drum. The longitudinal center of the tire band is marked with a suitable mark so that when the center of the tire band reaches the center of the tire building drum the mark is detected with a suitable sensor and the air stream through the air nozzle is terminated. The band applier is then axially retracted away from the tire building drum and collapsed for receiving a further tire band.
Details pertaining to the tire building drums of the type which may be satisfactorily used in combination with the band applier as modified by the present invention are set forth in U.S. Pat. Nos. 3,375,154; 4,636,277; and 4,780,171. These references are incorporated herein by reference.
While the band applier as previously constructed and as generally described above provided a mechanism for applying tire bands onto tire buildings drums there was found to be some attendant shortcomings or problems which detracted from the overall efficiency and operability of the band applier. These problems were primarily due to the lack of suitable control over the extent of and timing of the expansion of the band applier in order to provide the latter with the proper diameter required for applying the tire band carried by the band applier onto the tire building drum and without stretching the band by an unnecessary amount. Importantly, the individual bands, when relaxed after being stretched, do not rebound fully to their prestretched dimensions. Thus, for example, if the band on the band applier was expanded to a diameter more than about four inches greater than the outer of diameter of the tire building drum and any tire bands previously placed thereon, the band often would not rebound and thus being oversized, wrinkles occurred in the applied band due to over expansion of the band. Also, changes in the band ply angle occurred. These wrinkles, which are troublesome and difficult to remove, considerably detract from the efficiency of the band applier. On the other hand, if the band applier was not expanded sufficiently, i.e., to a diameter less than the outer diameter of the tire building drum and any band previously applied thereon, the tire band may not be displaceable from the band applier onto the tire building drum. Another problem was found to be present in the timing of the radial expansion of the band applier when using the air nozzle to facilitate the moving of the band onto the tire building drum. This problem arises when the band applier is not expanded sufficiently during the axial or longitudinal displacement of the band applier towards the tire building drum to permit the passage of the air nozzle over the outboard end of the tire building drum and any bands thereon so as to cause the air nozzle to impact against the end of the tire building drum and effectively interrupt the tire building operation. A further difficulty was experienced when using tire building drums of different diameters due to the problems encountered in adjusting the roller diameter to the outer diameter of the tire building drum within a fairly wide range of diameters.
These problems or shortcomings were also found to be increasingly difficult to overcome during the building of multiple-ply tire carcasses requiring the placement of several tire bands on the tire building drum since the effective diameter of the tire building drum increased with the application of each tire band. Also, with the application of each tire band, the space between the outboard end of a tire building drum and a band applier during its axial displacement towards the tire building drum was decreased by the thickness of the tire band. This decrease in space required that sufficient expansion of the band applier be achieved at a time sooner than that required for a previously applied band in order to assure passage of the air nozzle over the outboard end of the tire building drum and any tire bands thereon.